you can´t actually go to Es Vedra, those are the 2 rocks outside Cala D´Hort, but you can visit Es Cana instead (probably what you ment)...
Formentera, go by boat, see the spotlight section for more info.
if you did mean es vedra, then you can either park the car and walk to the edge of the cliffs above cala d'hort for some spectacular views (the es boldado restaurant is superb for this) or take a cruise around the islands es vedar and es vedranell from san antonio harbour. normally takes a few hours, with a beach bbq thrown in if you are lucky - if the weather is nice that is one fun day!
otherwise like ibiza-girlie says - check out our main site for more info about formentera.
p.s. we have a great search function by google - it really does find everything in our site.
If you are up and about on a Sunday morning, what about the church as San Jose with it's "Golden Altar" and see some of the real residents of Ibiza.
Alternatively, for island culture, get to San Carlos on a Saturday and visit the Las Dalias market and see some of the original hippy wares - each to their own, but I think it is much better than the Es Canar market on a Wednesday.